Angioedema is a swelling similar to hives, but the swelling is beneath the skin rather than on the surface. The swellings are called welts.

See also: Hereditary angioedema

Angioedema may be caused by an allergic reaction. It is associated with the release of histamine and other chemicals into the bloodstream. The body releases histamine when the immune system detects a foreign substance called an allergen.

Sometimes the cause of angioedema is never found.

The following items may cause angioedema.

• Animal dander (scales of shed skin)
• Certain medications (drug allergy)
• Emotional stress
• Exposure to water, sunlight, cold or heat
• Foods (such as berries, shellfish, fish, nuts, eggs, milk, and others)
• Insect bites
• Pollen

Hives and angioedema may also occur after infections or illness (including autoimmune disorders, and leukemia).

There is a form of angioedema that runs in families and has different triggers, complications, and treatments. This is called hereditary angioedema, and is not discussed here.

The main symptom is the sudden development of red welts. The welts usually occur around the eyes and lips. They may also be found on the hands, feet, and throat.

The welts are painful and may be itchy. They turn pale and swell if irritated.

Other symptoms may include:

• Abdominal cramping
• Breathing difficulty
• Swollen eyes and mouth
• Swollen lining of the eyes (chemosis)

The doctor will look at your skin and ask you if you have been exposed to any irritating substances. A physical exam might show stridor (crowing sound when inhaling) if the throat is affected.

Rarely, allergy testing may be performed.

Mild symptoms may not need treatment. Moderate to severe symptoms may need treatment. Breathing difficulty is an emergency condition.

Cool compresses or soaks can provide pain relief.

Medications used to treat angioedema include:

• Antihistamines
• Anti-inflammatory medicines (corticosteroids)
• Cimetidine (Tagamet)
• Epinephrine
  • Terbutaline (a bronchodilator)
  • Tranquilizers
• Sedatives

If the person has trouble breathing, seek immediate medical help. See: Breathing difficulties - first aid

At the hospital, a tube may be placed in the throat to keep the airway open.

Angioedema that does not affect the breathing may be uncomfortable, but is usually harmless and goes away in a few days.

• Life-threatening airway obstruction (if swelling occurs in the throat)
• Anaphylactic reaction

Call your health care provider if you have never had angioedema before, if it is severe, or does not respond to treatment.

Go to the emergency room or call the local emergency number (such as 911) if difficulty breathing, wheezing, stridor, or fainting occurs with an episode of angioedema.

To prevent angioedema from coming back, you should avoid irritating the affected area, stay away from known allergens, and avoid temperature extremes.

Never take medications that are not prescribed for you.

Kaplan AP. Angioedema. J Am Acad Dermatol. Sept 2005; 53(3): 373-88.

Habif TP. Clinical Dermatology. 4th ed. St. Louis, Mo: Mosby; 2004:129.

Marx J. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 5th ed. St. Louis, Mo: Mosby; 2002:1623.